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2025 Guide: How to Get Planning Permission for a House Extension in London

📝 Step 1: Know If You Need Planning Permission

Not all extensions need planning permission. Some fall under Permitted Development (PD) — a set of rights that allow minor extensions without full planning approval.


You can use PD if:

  • The extension is under 3m (semi or terrace) or 4m (detached)

  • Materials match the existing property

  • No balconies, verandas, or raised platforms

  • It doesn’t cover more than 50% of the garden

  • Not in a Conservation Area, flat, or Article 4 zone

✅ For 6m or 8m rear extensions, you can apply under the Neighbour Consultation Scheme (Prior Approval).


⚠️ Important: Many West London boroughs, like Richmond and parts of Hounslow, have Article 4 directions that remove PD rights.


🧱 Step 2: Decide the Type of Extension

Each extension type has different planning implications:

Extension Type

Planning Needed?

Rear Single Storey

Often under PD / Prior Approval

Side Infill

Usually full planning

Wraparound Extension

Always full planning

Double Storey Extension

Full planning

Loft + Extension Combo

Full planning + structural calcs

We can advise the best route depending on your property type, location, and council policies.



📐 Step 3: Prepare Planning Drawings

A professional planning application must include:

  • Existing & proposed floor plans

  • Elevations and sections

  • Site plan and block plan

  • Design & Access Statement (if required)

  • Planning application form (via Planning Portal)


💡 SY Design Studio handles all drawings, form submissions, and liaison with the council. We also advise you on how to maximise internal space while staying compliant.



📤 Step 4: Submit the Application

We submit the application via the Planning Portal and manage it through your local authority (e.g. Hounslow, Ealing, etc.).

The process includes:

  • Application validation

  • 21-day neighbour consultation

  • Case officer site visit (sometimes)

  • Decision within 8 weeks


You’ll receive a decision notice — Approved, Refused, or Request for Amendments.


🔁 Step 5: Amend or Appeal (if needed)

If refused, we’ll:

  • Review the officer’s feedback

  • Amend the design to meet policy

  • Re-submit the application

  • Or lodge a planning appeal (if appropriate)


✅ Planning Permission Secured? Now for Building Control


Once planning is approved, you’ll still need:

  • Building Regulations Drawings

  • Structural Calculations (steel beams, padstones, etc.)

  • Build-Over Agreements (if near a drain)

  • Party Wall Notices (if adjoining a neighbour)


SY Design Studio can handle all stages — from planning to building control and even structural design.


📍 Recent West London Projects:

✅ 6m Rear Extension in Southall – Approved via Prior Approval✅ Double-Storey Extension in Hounslow – Approved under full planning✅ Side Infill + Loft in Ealing – Full application + building control drawings


Want us to review your extension idea for FREE? Just send us your postcode and a photo of your rear garden.

💬 Client Review

"The team at SY Design Studio were brilliant from start to finish. Our planning application was approved on the first attempt — and their drawings were spot on for our builder to work from!"— Mr. Patel, Ealing


📞 Ready to Extend Your Home?


Let us handle everything — planning drawings, structural design, and council submissions.


👉 Visit www.sydesignstudio.co.uk📞 Call us for a free quote today📍 Based in Hounslow | Serving West London & Surrounding Areas

 
 
 
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